Jet propulsion unit for boats

ABSTRACT

This invention provides a water jet propulsion unit for boats which has a ducted impeller driven by an internal combustion engine mounted on top of the unit, the impeller having a vertical axis and directing a water jet rearwardly through an elbow duct. Cooling water is bled from the elbow duct upwardly to flow over surfaces at the upper end of the unit which are heated by the engine, this water mixing in an upper chamber with engine exhaust gases before travelling downwardly through a second duct to a chamber surrounding the elbow duct, from which the cooling water and exhaust gases escape through apertures facing in the same direction as the jet nozzle.

United States Patent 1191 Giacosa 1451 Aug. 7, 1973 [73] Assignee: Sira Societa Industriale Ricerche Automotoristiche, Turin, Italy [22] Filed: Apr. 27, 1972 [21] Appl. No.: 248,145

[75] Inventor:

[30] Foreign Application Priority Data May 11, 1971 Italy ..,..68558A/71 52 us. c1. 115/17, 115/12 A 51 1111. (:1 B63h 21/00 58 Field of Search 115/11, 12 R, 12 A,

115/17, 18 R, 18 A, 18 B; 60/221, 222; 239/265.17, 265.19

[56] References Cited UNITED STATES PATENTS 2,743,698 5/1956 Leonard et al. 115/16 3,310,022 3/1967 Kollman 115/17 FOREIGN PATENTS OR APPLICATIONS 567,569 2/1945 Great Britain 115/12 A 1,071,054 6/1967 Great Britain 115/12 A Primary Examiner-Milton Buchler Assistant Examiner-Jesus D. Sotelo Attorney-Richard C. Sughrue, Robert V. Sloan et al.

{57] ABSTRACT This invention provides a water jet propulsion unit for boats which has a ducted impeller driven by an internal combustion engine mounted on top of the unit, the impeller having a vertical axis and directing a water jet rearwardly through an elbow duct. Cooling water is bled from the elbow duct upwardly to flow over surfaces at the upper end of the unit which are heated by the engine, this water mixing in an upper chamber with engine exhaust gases before travelling downwardly through a second duct to a chamber surrounding the elbow duct, from which the cooling water and exhaust gases escape through apertures facing in the same direction as the jet nozzle.

3 Claims, 7 Drawing Figures PATENTEmus Han 3.750.614

SHEET 1 OF 4 PATENTEUAUS 7 ms SHEEI 3 OF 4 r7- 14aD JET PROPULSION UNIT FOR BOATS BACKGROUND OF THE INVENTION This invention relates to jet propulsion units for boats.

More particularly, the invention concerns water jet propulsion units of the type comprising a substantially tubular body mounted rotatably on a pivotal support adapted to be fixed to the stern plate of the boat, the tubular body housing a substantially vertical transmission shaft which is driven by an internal combustion engine located at the top of the body and which drives an impeller having helical blades located at the lower end of the body. The impeller acts as a pump, drawing water from a lower inlet facing in the direction of desired movement and expelling the water as a jet from a nozzle facing in the opposite direction to the direction of movement to give rise to a reaction which propels the boat in the desired direction.

An object of this invention is to provide a jet propulsion unit of the abovementioned type in which hot parts of the driving engine are effectively cooled by withdrawing part of the water pumped by the impeller and using this cooling water to assist in silencing the exhaust of the engine.

Another object of the invention is to provide a pro pulsion unit of the abovementioned type which has high hydraulic efficiency and in which the discharge of the cooling water is used to increase the reactive propulsion thrust.

A further object of the invention is to provide a propulsion unit of the abovementioned type in which transmission of engine vibration to the boat being driven is reduced to a minimum.

SUMMARY OF THE INVENTION According to this invention there is provided a jet propulsion unit for boats of the type comprising a tubular body rotatably mounted in a fixed support adapted to be attached to a boat, means for mounting an internal combustion engine on the said body, a transmission shaft adapted to be coupled to the engine and drivingly connected to a bladed impeller situated in a tubular casing the axis of which is coaxial with said transmission shaft, and a water inlet communicating with said casing and with a discharge nozzle which discharges water pumped by the impeller in a direction opposite to the desired direction of advance, characterised in that an elbow duct interconnects the tubular casing in which the bladed impeller is located and the discharge nozzle, and in that a first annular duct surrounding the transmission shaft extends from the elbow duct to the upper part of the tubular body for the conduction of cooling water to parts of the unit which in use receive heat from the engine and to an upper chamber into which a conduit adapted to receive the engine exhaust gases leads and in which the exhaust gases mix with the cooling water, and in that a second annular duct coaxial with the first annular duct leads from the upper chamber to an intermediate chamber which surrounds the elbow duct and which communicates with the exterior through apertures facing in the same direction as the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more clearly understood from the following detailed description, given by way of nonlimiting example, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic lateral elevation of ajet propulsion unit according to one embodiment of the invention;

FIG. 2 is a front elevation of the jet propulsion unit shown in FIG. 1;

FIG. 3 is a rear elevation of the said jet propulsion unit;

FIG. 4 is a longitudinal section of the said unit on a slightly enlarged scale, taken on line IV IV of FIG.

FIG. 5 is a longitudinal section on a further enlarged scale of a part of the unit as shown in FIG. 4;

FIG. 6 is a transverse cross section on an enlarged scale, taken on line VI VI of FIG. 4, and

FIG. 7 is another longitudinal section taken on line VII-VII of FIG. 4.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to the drawings, a jet propulsion unit according to the invention, indicated generally by 1, comprises a tubular support 2 provided at its rear with a radial fin 3 and having a forwardly projecting lug 4 by means of which the unit 1 is pivotally attached to a C- shaped frame 6 by means of a horizontal pivot pin 5, the frame 6 having screw clamp means permitting its attachment to the stern transom of a boat (not shown).

A tubular body 8 is rotatably supported by means of bear sleeves 7 within the tubular support 2. The tubular body 8 is connected at its upper end to a shell 9 which is connected by way of bushes 10 of elastomeric material to a moulded casing 11 enclosing an internal combustion engine, shown diagrammatically in broken outline at 11A in FIG. 1.

Within the rotatable tubular body 8 there is arranged coaxially a tubular conduit 12 connected at its upper end to a sleeve 13 (FIG. 5) provided with integral transverse flanges l4 and 14a which constitute the upper wall of an upper chamber E defined within the shell 9. An exhaust conduit 15 for the combustion products of the engine 11A enters the rear end of the chamber E, the conduit 15 forming part of a transverse diaphragm 16 which is spaced from the flanges 14, 14a and which defines therewith a transverse duct D.

A tubular coupling 17 is housed within the sleeve 13 and defines therewith an annular passage C. The coupling 17 has an upper internally splined end in which an externally splined end of the crankshaft 18 of the engine 11A engages, and a lower internally splined end in which an upper externally splined end of a vertical transmission shaft 19 engages, the shaft 19 extending coaxially, with considerable radial clearance, within the bore of the tubular conduit 12.

Below the tubular support 2 there is arranged a hollow downwardly flared casing 20 for the intermediate part of the propulsion unit. The casing 20 is connected at its lower end to a tubular casing 21 which in turn terminates at its lower end in an aperture 22 inclined towards the direction of movement and constituting a dynamic water inlet. The inlet aperture 22 is traversed by a central beam 23 to which a plurality of vanes 24 are attached for directing the water flowing into the aperture 22 through a helical bladed impeller 25 attached to the lower end of the transmission shaft 19 and housed coaxially within the tubular casingZl.

immediately above the impeller 25 there is arranged a bladed rectifier 26 comprising static blades attached to the casing 21 which convert the kinetic energy imparted by the impeller 25 to the water into pressure energy. The rectifier 26 communicates with a convergent discharge duct 27 in the shape of a right-angled elbow which terminates in a rearwardly-facing discharge nozzle 28 with a horizontal axis, through which the water is expelled outwards to provide the propulsive reaction thrust. The duct 27 and nozzle 28 are contained in the intermediate casing within which a space is defined which is subdivided into three chambers G, H, l. The chambers G and I communicate with the exterior through rearwardly facing apertures 32, 33 situated respectively above and below the nozzle 28.

A tubular lower conduit 29 extends upwardly from the elbow-shaped duct 27. The conduit surrounds the transmission shaft 19 and is connected to the tubular conduit 12, so that between the shaft 19 and the said two conduits 12, 29 there is defined a first annular duct B, B along which part of the water pumped by the impeller ascends, flowing over the splined joint in the annular passage C into the transverse duct D to cool the hot parts of the engine 11A. The flow of water is reversed in the upper chamber E of the casing 9 where the cooling water, indicated by white arrows in FIG. 5, becomes mixed with the engine exhaust gases coming from the conduit 15 and indicated by black arrows in FIG. 5.

The rotatable tubular body 8 is connected at its lower end to a tubular member 30, of the same diameter as the body 8, located coaxially within the casing 20. The upper part of the casing 20 is reinforced internally by transverse walls 31 provided with orifices. A second annular duct F, F is defined between the body 8, the member and the conduit 12. The cooling water mixed with engine exhaust gases descends through the second duct F, F to enter the chambers G, H, 1, surrounding the elbow duct 27. This cooling water/exhaust gas mixture flows out through the apertures 32 above the nozzle 28 or through the apertures 33 below the nozzle, after flowing over the outside of the duct 27. The water issuing from the apertures 33, which are located below the waterline A in use of the motor, contributes to the propulsive thrust supplied by the water jet flowing from the propulsion nozzle 28. The apertures 32 located above the nozzle 28 permit discharge of most of the engine exahust gases, since the discharge of these gases through the lower apertures 33 is impeded by the fact that the latter are below the waterline A.

The entire motor unit is rotatable about a vertical axis to permit steering of the boat by rotating the assembly constituted by the top shell 9, to which the engine 11A is connected in use of the unit, the tubular body 8 and the casings 20 and 21, with the components mounted therein.

it will be understood that the manner of operation and the constructional details of practical embodiments of the invention may be .varied widely from the embodiment herein described and illustrated, without thereby departing from the scope of this invention.

What is claimed is:

1. Jet propulsion unit for boats of the type comprising a fixed support, means for attaching said fixed support to a boat, a tubular body rotatably mounted in said fixed support, mounting means for an internal combustion engine on the upper part of said body, a transmission shaft adapted to be coupled at one end to said engine, a bladed impeller connected to the other end of said shaft, a tubular casing housing said impeiler, the axis of said casing being coaxial with said transmission shaft, water inlet means communicating with said casing and a discharge nozzle connected to said casing and arranged to discharge water pumped by said impeller in a direction opposite to the desired direction of ad vance, wherein the improvement consists in:

an elbow duct interconnecting said tubular casing and said discharge nozzle,

3 first annular duct surrounding said transmission shaft and extending from said elbow duct to the upper part of said tubular body, said first duct conducting cooling water to parts of the unit which in use receive heat from said engine,

means defining an upper chamber communicating with said first duct to receive cooling water therefrom,

a conduit adapted to receive the engine exhuast gases and extending into said upper chamber, the engine exhaust gases mixing with the cooling water in'said chamber in use of the unit,

a second annular duct coaxial with said first duct and leading from said upper chamber, and

an intermediate chamber communicating with said second duct and surrounding said elbow duct, said intermediate chamber having apertures communicating with the exterior and facing in the same direction as said nozzle. I

2. Jet propulsion unit as claimed in claim 1, including a moulded external casing containing said elbow duct and said nozzle, said external casing being interposed between said impeller casing and said fixed support.

3. Jet propulsion unit as claimed in claim 2, wherein said first annular duct through which the cooling water rises is formed by a tubular lower conduit connected to said elbow duct, an intermediate conduit and a sleeve provided with external transverse flanges, a transverse diaphragm defining with said transverse flanges a transverse duct adapted in use of the unit to receive heat from said internal combustion engine, and wherein said second annular duct through which the cooling water descends is formed by a tubular member situated within said external casing and by said tubular body, the latter being connected at its upper end to said upper chamber in which the engine exhaust gases mix with said cooling water. 

1. Jet propulsion unit for boats of the type comprising a fixed support, means for attaching said fixed support to a boat, a tubular body rotatably mounted in said fixed support, mounting means for an internal combustion engine on the upper part of said body, a transmission shaft adapted to be coupled at one end to said engine, a bladed impeller connected to the other end of said shaft, a tubular casing housing said impeller, the axis of said casing being coaxial with said transmission shaft, water inlet means communicating with said casing and a discharge nozzle connected to said casing and arranged to discharge water pumped by said impeller in a direction opposite to the desired direction of advance, wherein the improvement consists in: an elbow duct interconnecting said tubular casing and said discharge nozzle, a first annular duct surrounding said transmission shaft and extending from said elbow duct to the upper part of said tubular body, said first duct conducting cooling water to parts of the unit which in use receive heat from said engine, means defining an upper chamber communicatinG with said first duct to receive cooling water therefrom, a conduit adapted to receive the engine exhuast gases and extending into said upper chamber, the engine exhaust gases mixing with the cooling water in said chamber in use of the unit, a second annular duct coaxial with said first duct and leading from said upper chamber, and an intermediate chamber communicating with said second duct and surrounding said elbow duct, said intermediate chamber having apertures communicating with the exterior and facing in the same direction as said nozzle.
 2. Jet propulsion unit as claimed in claim 1, including a moulded external casing containing said elbow duct and said nozzle, said external casing being interposed between said impeller casing and said fixed support.
 3. Jet propulsion unit as claimed in claim 2, wherein said first annular duct through which the cooling water rises is formed by a tubular lower conduit connected to said elbow duct, an intermediate conduit and a sleeve provided with external transverse flanges, a transverse diaphragm defining with said transverse flanges a transverse duct adapted in use of the unit to receive heat from said internal combustion engine, and wherein said second annular duct through which the cooling water descends is formed by a tubular member situated within said external casing and by said tubular body, the latter being connected at its upper end to said upper chamber in which the engine exhaust gases mix with said cooling water. 